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The COVID-19 pandemic has led to a dramatic loss of human life worldwide and presents an unprecedented challenge to public health systems. The economic and social disruption caused by the pandemic is devastating.
Another menace that has been recognized as an complication of this viral infection is a rare fungal infection – MUCORMYCOSIS. The infection due to this fungus has been very rare and this invasive disease is still less understood.
Worldwide Incidence of 6/100 000 cases/year with increasing incidence every year along with increased mortality due to increase in the prevalence of diabetes, organ transplants and cancers. It is the fourth most common infection in the patients receiving intensive care treatment. The mortality rate is around 50% but with early diagnosis and appropriate treatment up to 80% of the affected can be saved.
What is Mucormycosis or Black Fungus?
Mucormycosis is an aggressive, invasive, granulomatous, acutely infective and opportunistic infection that is caused by members of the Phycomycetes class of fungi.
Rhizopus oryzae is responsible for 70% of the reported cases of Cerebro- rhino-orbital Mucormycosis (CROM). Organisms are airborne and can be found in locations such as bread mold, soil, manure and decaying vegetables. This can involve a number of organs such lung, kidney, bones , bladder. GIT, skin, heart , brain.
CROM is the most common type of Mucormycosis. Iron metabolism plays a major role in the regulating the disease. Des feroxamine predisposes to Mucormycosis by inappropriately supplying iron to the fungus. The elevated levels of irons in patients makes them more susceptible to the infection. Ketoacidosis, low oxygen concentration and hyperglycemia provide an excellent medium for disease due to active ketone reductase system in Rhizopus . Even immuno-competent hosts can develop the infection. The exact mechanisms by which phagocytic function is impaired by ketoacidosis, diabetes mellitus, and corticosteroids is yet to be determined. Phagocyte dysfunction alone cannot explain the high incidence of Mucormycosis among patients with DKA, because the incidence of Mucormycosis among these patients is more than the incidence of infections caused by other pathogens. Therefore, Mucorales must possess unique virulence traits that causes the organism to exploit state of immunosuppression and physiologic impairment seen in this subset of patients.
There are a number of risk factors for developing the disease such as – chronic use of antibiotics and immunosuppressive drugs such as steroids, metabolic abnormalities such ad diabetic ketoacidosis, hematological malignancies, chronic renal failure, cancers, AIDS, states of iron and aluminum overload, hepatic failure, trauma, burns, desferoxamine therapy in patients undergoing hemodialysis.
The infection is characterized by angioinvasion which leads to thrombus formation and eventually leads to necrosis due to compromised blood supply. The decreased blood supply to the infected organs also compromise the action of leucocytes and the action of antifungals in the affected areas. The organism has a propensity for dissemination to other organs due to its affinity for the blood vessels.
The disease can involve any age group , sex, race or occupation. The common non ocular symptoms of CROM are facial numbness, facial swelling, nasal blockage, bloody nasal discharge, pain in teeth or pain during chewing, swelling on the hard palate, blackening of the palate or perforation, facial palsy, hemiplegia, decreased mental function. The disease is usually unilateral and remains so in most of the cases but bilateral cases do occur. The orbital symptoms are lid and periorbital swelling, eyelid abscess, ptosis, chemosis, corneal oedema, decreased vision, proptosis, ophthalmoplegia, involvement of multiple cranial nerves and cavernous sinus thrombosis.
Clinical progression of CROM
- Stage 1-infection of the nasal mucosa and the sinuses
- Stage 2-orbital involvement(orbital apex syndrome, superior orbital fissure syndrome)
- Stage 3-cerebral involvement in which intracranial spread occurs via one of the following routes
- Ophthalmic artery
- Superior orbital fissure- sinus thrombosis, internal carotid artery thrombosis
- Cribriform plate- frontal lobes, cavernous sinuses
Diagnosis is dependent on the clinical features, imaging techniques, mycological and histopathological findings. KOH staining of the tissue or secretions reveal the typical aseptate branching fungal hyphae which are typical of this invasive infection. Further, culture can specify the species and antifungal susceptibility.
Both CT and MRI can be used for radiological diagnosis. CT reveals soft tissue involvement, mucosal thickening, bone erosion and necrosis and intra cranial and cavernous sinus involvement.
MRI provides for better delineation of the blood vessel involvement and intracranial extension of the infection, infiltration of the orbital fat and orbital cellulitis.
Management of Black Fungus
Successful management depends on the timely diagnosis of the infection, the reversal of the underlying predisposing factors, early and ideal broad surgical debridement and the rapid initiation of the systemic antifungal therapy.
Aggressive surgical debridement coupled with the excision of localized lesions because the vascular thrombosis prevents systemically administered drugs from reaching the infected tissues. Serial imaging is important in disease management to assess the progress of the disease. Since the disease is vaso-occlusive the debrided tissues rarely bleed , and the end point for the debridement is until the fresh bleeding tissue is observed. Although the treatment of the disease by surgical means may cause loss of vision and disfigurement of the face and difficulty in swallowing and can have severe psychological ramifications for the patient. But reconstructive surgery following complete resolution of disease and other restorative measures can offer some solace to the patient. The current trends in aggressive management of the disease can significant affect the outcomes of the disease.
The medical management is consists of administration of intravenous antifungals with close monitoring of the renal parameters and serum electrolytes. The drug of choice for the treatment is amphotericin which is available in various forms. The lipid formulations are preferred over the amphotericin deoxycholate considering the renal toxicity with the later the other drugs which are available are Posaconazole and Isovuconazole.
Early intervention both surgical and medical is crucial in determining the outcome of the disease. Adequate surgery and medical management is very important aspect of treatment of these patients.
This information is for general guidance and reflects the opinions and experience of the author. It is not intended to replace specialist consultation or provide treatment advice for specific cases.